Styling a form? (already have image)

How would i style a form?

I purchased Unique Table an Login Form Design - Graphics - GraphicRiver (only interested in the actual login form, username,password and submit, i can do the other stuff.

For the price table thingy and the form, but how would i go about doing this?

Can i just include the image and then put the html "on top" or would i have to use CSS? And how?

Thanks